Refining of hydrocarbon oils with hf and tif



Nov. l, 1955 A. P. LIEN ETA.

REFINING OF HYDROCARBON OILS WITH HF' AND TIF' Filed Aug. so, 1952 United States Patent F REFINING F HYDROCARBON OILS WITH HF AND TIF Arthur P. Lien, Highland, Ind., and David A. McCaulay,

Chicago, Ill., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application August 30, 1952., Serial No. 307,192

20 Claims. (Cl. 196-39) This invention relates to the refining of mixed hydrocarbon oils. More particularly, it relates to the refining of hydrocarbon oils containing, in addition to other hydrocarbon compounds, aromatics, organic surfur compounds, oxygenated compounds and nitrogen compounds. The invention is of particular interest to the treatment of hydrocarbon distillates boiling in the naphtha range in order to .recover therefrom benzene, toluene, Ca aromatic hydrocarbons, and higher boiling aromatic hydrocarbons.

Naturally occurring hydrocarbon oils are mixtures of various classes of hydrocarbons and various organic compounds containing one or more of the elements sulfur, oxygen and nitrogen. For some uses many hydrocarbon oils contain an objectionable amountof aromatic hydrocarbons, e. g., diesel oils, kerosenes, domestic fuel oils and lubricating oils. For some uses hydrocarbon oils should not only be low in aromatics, but also low in y organic sulfur compounds. In some cases such as coal tar distillate, the oil contains substantially only aromatics and some organic sulfur compounds, and it is desired to remove the sulfur compounds only. In the case of shale oil, it is desirable to remove not only sulfur compounds,

but also nitrogen compounds and oxygen compounds.`

is by treatment with liquid HF and silver fluoride as disclosed in U. S. 2,531,723.

Aromatic hydrocarbons exist in virtually all crude oils, The separation by fractional distillation of these aromatics from the non-aromatics, i. e., paraffins, naphthenes, organic sulfur compounds and-in the case of naphthas derived from thermal or catalytic cracking operationsolefns and oxygenated compounds such as alkylphenols, is extremely diiiicult because members of the various classes of hydrocarbons have similar boiling points. The

solvent extraction processes for improving the quality of lubricating oil fractions are not suitable for the recovery of aromatics boiling in the naphtha range. While liquid SO2 extraction has been adapted to benzene and toluene recovery, it suffers from the disabilities of operating at rather low temperature and relatively low percentage recovery. Now in commercial use are processes using extractive distillation or azeotropic distillation for the recovery of the aromatic hydrocarbons boiling in the naphtha boiling range, i. e., benzene, toluene, ethylbenzene and the xylenes. These processes all possess certain disabilities ranging from low percentage recovery to an inability to recover more than one substantially pure aromatic constituent in a given integrated process.

2,722,502 Patented Nov. 1, 1955 ICC voils containing objectionable amounts of these materials.

A further object is the refining of lubricating oil distillates to improve the viscosity index thereof. Still another object is the recovery of aromatic hydrocarbons from hydrocarbon mixtures boiling in the naphtha range, i. e., below about 450 F. A particular object of this invention is the treatment of yan aromatic-containing naphtha which boils below about 325 F. to obtain the aromatic hydrocarbon portion thereof substantially free of interfering non-aromatic materials in order that individual aromatic compounds or close-boiling groups of compounds may be recovered therefrom. Further objects will become apparent in the detailed description of the invention.

It has been discovered that the objects of this invention can be attained by treating hydrocarbon oils which contain appreciable amounts of aromatic hydrocarbons, and/ or organic sulfur compounds, and/ or phenolic compounds, and/or nitrogen compounds by treating said hydrocarbon oils with thallium monofluoride--TlF-in the presence of a sutlicient amount of substantially anhydrous vliquid HF to form a separate HF-rich phase.

TIF is avcrystalline solid having a boiling point of 570 F. It has been discovered that the solubility of TIF in liquid HF is enormously increased when Van aromatic hydrocarbon, organic sulfur compound, or phenolic compound is brought into contact with the TlF, in the presence of liquid HF. For example, a mixture of solid TlF 4and liquid HF is'rapidly converted to a clear, homogeneous liquid when themixture is contacted with a sufficient amount of benzene or xylene.

The solubility of lower molecular weight mononuclear aromatic hydrocarbons in liquid HF at ambient temperatures is quite low, e. g., at 70 F., benzene and xylene are soluble to the extent of 3 volume percent. It has been discovered that more of these aromatic hydrocarbons can be taken up by liquidv HF in the presence of TIF than the liquid HF is capable vof dissolving in the absence of T 1F. It is believed that this increase in solubility is'due to the formation of a complex consisting of the aromatic hydrocarbon, HF and TlF. (Aromatic hydrocarbons and TlF do not form a complex in the absence of liquid HF). This complex is extremely soluble in liquid HF and it is possible to have enormously more TlF and aromatic hydrocarbon present in a complex-liquid yHF solution than liquid HF alone is capable of dissolving. This complex is stable in the presence of liquid HF at ambient temperatures. However, the components of the aromatic hydrocarbon complex can be recovered readily by distilling the HF and the aromatic hydrocarbon whereupon the TlF remains behind in the form of a very finely divided solid.

Within the limits of experimental error it has been found that 1 mol of TIF and 1 mol of aromatic hydrocarbon such as benzene, toluene, xylene or ethylbenzene are present in each mol of TlF-aromatic-HF complex. The exact content of HF is unknown, but is believed to be 1 mol per mol of complex.

It has been found that when` a mixture of aromatic hydrocarbons-such as benzene, toluene, xylene and ethylbenzene-and non-aromatic hydrocarbons is treated with a solution of TIF in liquid HF, an upper raffinate phase and a lower extract phase is obtained. The upper rai'lnate phase consists of a very small amount of liquid HF and a mixture of hydrocarbons, which mixture contains a smaller percentage of aromatics than vthe feed mixture. The 'extract phase consistsof liquid HF, complex, and physically dissolved aromatic and non-aromatic hydrocarbons; the extracted hydrocarbons recovered from `ofHF-for eachmol of `aromatic in the feed mixture will not remove more Lthan 80 to185% of the total aromatics .therein,1in.a single contacting stage.

When lvery high percentage ,recoveriesare desired of the aromatic hydroicarbons `contained in a hydrocarbon distillate boiling in the naphtha range, the maximum amount of TlF should .beusedgthisamount corresponds to 1 mol per mol of aromatic'hydroarbons inthefeed plus the amount of TlF that anbephysieally dissolved `by the complex containing` liquid It is preferred to operate with an amount of .'IlFgsomewhatrless Ythan that amount which results intheforrnation of a separate solid .TIF phase as no beneficial ,results are obtained by the presence of the solidflflF, lanidseriolus operational ditculties may (result. t The amount of TlFused will depend on the amount of `aromatic ,extraction desired. When treating naphthas the amountof TIF may beas little as 0.1 molper mol of r 4aromatic hydrocarbon `in the feed. 4s peak of 'the `usage of TlF in terms of mols per mol of It is preferred to aromatic hydrocarbon.that is to be extracted, i. e., when less than the maximum amountof extraction lis desired.

Some gain in extraction eticiency is obtainable by the use :of continuous countercurrent contacting or batch ,multi-.stage 1 contacting. Normally a single contacting .stage provldedwith adequate mixing produces results that are almost as good as those obtained with multi-stage contacting When using single-stage contacting for maximum extraction of aromatic hydrocarbons, the maximum amount of TlF should be used. I

`It snecessary to have present in the treatingzone an amount of liquid HF sufficient to participate in the formation of the TlF containingcomplex, i. e., 1 mol per mol Aof flvlFlpresent. .In addition to this amount it is necessary to have additional liquid HF present in order to gdlssolvethecomplex that `has been formed andto permit the separation of the complex as the solution in the liquid HF. Of course suicient liquid HF must be presentl to producela separate liquid HF-rich extract phase. The

l,extract phase'consists of complex, aromatichydrocarbons and nonaromatic hydrocarbons in simple solution and excess HF. Although the ,minimum amount of liquid needed depends somewhat on the amount of aromatic hydrocarbon `that is to be extracted from a mixed hydrocarbon feed, it has been found that phase separation can -be obtained when using as little as volume percent of liquid HF, based on total feed. Larger amounts of liquid HF Iup to 1500 volume `percent or more, based on feed, may be used. It is preferred to use between about 100 andf 500 volume percent of liquid HF, based on feed.

yIt has been found that the presence of water has adetrimental effect on the process of this invention. The process should be carried out rundersubstantially anhydrous conditions and the liquid HF used should'be substantially anhydrous, i. e.,`the liquid HF should `not containmore than 2 or 3% of water.

tNon-aromatic hydrocarbons are only veryrslightly soluble in liquid HF; they are somewhat more `soluble in liquid HF containing the aromatic-TlF-HF complex. Apparently the complex solubilizes both aromaticA hydrocarbons and non-aromatic hydrocarbons so that more of these hydrocarbons can be taken up by the liquid HF than would be predicted by the solubility -of the hydrocarbons in pure liquid HF. However, 4this solubilizing effect at constant TIF level appears to be a UIEQD. 0f

-phase along with the non-alkylated aromatics.

the concentration of the complex in the liquid HF because, surprisingly enough, it has been discovered that the amount of non-aromatic hydrocarbon present in the extract hydrocarbons is lower at large liquid HF usage than at small liquid HF usage. The amount of nonaromatics present in the extract hydrocarbons at the same TIF concentration can be reduced to an ordinarily unobjectionable amount of 2-3% in a single stage `by using about 300% or more of v-liquid HF based on total feed.

Temperaturesas low as 60 F. `may be `used if theresultant increase in viscosity is not `considered `to vbe disadvantageous. At higher temperatures, e. g., Z50-300 F., the HF catalyzes the isomerization and even cracking of the paraffns and .naphthenes normally present in naphthas derived from petroleum sources. In general temperatures are maintained between about 0 and 160 F. and it is preferred to operate at ambient temperatures, i. e., between 30 and about 100 F. In order to keep the 'HF in the liquid state, suicient pressure must be maintained on the extraction system to ensure this condition at the Vtemperature of operation; e. g., at 160 F., about p. s. i. g.

`For best results the feed stock and the solvent should be contacted for a time long enough to permit maximum recoveryl of aromatics by the particular amount of TIF present in the treating agent. The length of time needed `for this yamount of contacting `in large part will depend upon the leificiencyof the contacting device. When operating at ambient temperatures, contacting times in ex- ,CCSSof the minimum necessary for desired amount of recovery are not harmful. In general it has been found that with efficient mixing, good results can be obtained at contact times between about five minutes and six hours.

Organic-sulfur compounds, such as are normally present in most petroleum naphthas, form complexes with TlF ,in the presence of liquid HF. These complexes ,appear to be more diicult to decompose than the TIF aromatic complexes. However, the complex can be dissociated by heating to a temperature on the order of 40C-,500 F. These sulfur-compound complexes appear `to emulsify liquid HF and the hydrocarbons, making phase separation very diicult and, in some cases, gravity separation alone is not suicient. The larger theamount of sulfur in thenaphtha to be treated, the more likely it is that separation difficulties will be encountered. In ygeneral it is preferred to operate on hydrocarbon mixtures which contain essentially no sulfur compoundson the order of less than .02 wt. percent sulfur. Naphthas containing a sulfur content suitable for this process can be readily obtained-by treating high sulfur naphthas with liquid HF or by hydrodesulfurization or by hydroforming or by anyother process that removes sulfur without simultaneously removing appreciable quantities of the dcsired aromatics.

-In general olefins, in the amounts usually present in naphthas that would be desirable feed stocks to this process, do--not interfere with separation of the extract phase from the ratnate phase. It has been found that the aromatic compounds present are alkylated by the ole- -ns-inthe feed stock to form alkylaromatics which complexwith TIF and which are recovered in the extract These alkylated aromatics boil above xylenes and can be readily separated from xylenes by simple fractional distillation.

`No Vappreciable vformation of alkyluorides has been ob- `can beA use cll as aviation safety fuel blending stocks; or they may'fbe usedashigh` solvency naphthas.

The Vpl'lenolic-type materials found in most naphthas derived .fromthermal or catalytic .cracking react` with TIF to form complexes which are detrimental to phase separation. Also, thesematerials increase the dfculty of obtaining pure compounds by simple fractional distillation from the aromatics recovered by our process. However, one or two washes with a concentrated sodium hydroxide solution will reduce these phenolic compounds to a level where no appreciable hindrance to phase separation will take place. Another method of removing these phenolic bodies is to treat the raw naphtha with liquid HF.

This process may be applied to a mixture of hydrocarbons comprising aromatics, parafns, naphthenes and olefins which'boil in the naphtha range, i. e., below about 450 F. The presence of polyalkylbenzenes and polylnuclear aromatics in hydrocarbon distillates boiling above :about 450 F. renders very difficult the recovery of individual compounds or a group containing a small number of compounds boiling close together. The feed stock to this process must be free from HzS and substantially free of organic sulfur compounds, particularly those found in virgin naphthas derived from high sulfur crudes, such as West Texas crude. It is preferred that the feed stock contain less than about 0.02 wt. percent of sulfur. In general it has been found that a high sulfur naphtha which has been desulfurized by treatment with liquid HF is a satisfactory feed to our process. Naphthas containing appreciable amounts of materials boiling above 450 F. are more dicult to desulfurize by conventional methods to a level at which the sulfur compounds will not interfere with the separation of the feed stock into a raffinate phase and an extract phase. Naphthas boiling below about 325 F. are particularly suitable for this process because they are easily desulfurized and dephenolized and substantially pure Cs, C7 and mixed Ca aromatics are readily recovered therefrom.

A particularly suitable feed for this process is the naphtha derived from the so-called hydroforming process, i. e., the vapor phase treatment of a virgin naphtha at 8501050 F. in the presence of hydrogen over a catalyst such as molybdena on an alumina support or a platinumcontaining catalyst. The hydroformate from such a process is low enough in sulfur to permit operation without further desulfurization and is so low in olefin that very little of the benzene, toluene and Xylenes is degraded to higher boiling alkyl aromatics by alkylation.

By suitable pretreatment to remove interfering materials, this process for recovering high purity aromatic hydrocarbons can utilize naphthas boiling below about 450 F., and particularly those boiling below 325 F., derived from distillation of petroleum, the thermal or catalytic cracking of naphthas from pertoleum, naphthas derived by the hydroforming or hydrodesulfurization of virgin or cracked naphthas, or a mixture of aromatics, paranics, naphthenics and oleiinics derived from any source.

The usual naphtha feed stock to this process will contain 50 volume percent or more of non-aromatic material. Where aromatic concentrates are available from super fractionation equipment, feed stock containing 70 or 80% of benzene or toluene or Ca aromatics may be available. It has been found that when operating on feed stocks containing much in excess of 50% of aromatic hydrocarbons, it is desirable to add a diluent to the feed stock prior to the contacting step. The diluent should be a paraflinic and/ or naphthenic hydrocarbon or a mixture of hydrocarbons that is low in materials that would interfere with phase separation and that will be readily separable by simple fractional distillation from the individual aromatic hydrocarbons. It is preferred to use as diluents parafnic and naphthenic hydrocarbons of low boiling point since these materials are not isomerized or cracked by the liquid HF at the preferred operating temperatures. Suitable hydrocarbons are pentane, hexane, heptane, cyclohexane, methylcyclohexane, petroleum ether, etc. When operating at low temperatures such as 30 F. the diluents might be higher boiling paraffinic or naphthenic hydrocarbons containing 9, 10 or l1 carbon atoms." However, in general, the feed stocks to this proc- 6 ess will not require the use of a diluent. It is preferred to operate without diluent since the presence ofy high percentages of non-aromatic compounds requires the use of more TlF in order to obtain the same percentage extraction and more HF in order to maintain selectivity of extraction.

The non-aromatic hydrocarbons extracted fromy the feed by the treating agent boil in about the same range as the aromatic hydrocarbons. 'Iheir presence decreases the purity of the aromatic hydrocarbons and they must be removed in order to obtain substantially pure aromatics as the final product. It has been found that these nonarornatic hydrocarbons can be readily displaced from the extract phase by washing the extract phase with a diluent type hydrocarbon such as pentane, hexane or a 9, l0 or 1l carbon atom hydrocarbon. A single stage washing operation is usually sufficient to reduce the nonaromatic content of the extract phase to a point where nitration grade benzene or toluene can be made by simple fractional distillation of the recovered aromatic hydrocarbons.

It has further been discovered that the use of liquid HF-TlF treating agent markedly improves certain qualities of hydrocarbon oils boiling in the heavier-thangasoline range, i. e., from about 350 to about 700 F. The treatment is particularly effective in improving the burning quality of kerosenes and cetane number of diesel fuels when the raw oils contain objectionable amounts of aromatic hydrocarbons. Also, this treatment markedly improves the viscosity index of lubricating oils derived from naphthenic-type and asphaltic-type crudes.

It is believed that this quality improvement is obtained through the formation of a liquid HF-soluble complex of TIF and HF with the objectionable aromatic hydrocarbons, organic sulfur compounds and nitrogen compounds.

Some improvement in quality of the oil can be obtained by using even a trace amount of TlF and further irnprovements can be obtained by increasing the amount of TlF4 until substantially all the materials removable by the liquid HF-TIF treating agent have been removed. In general the larger the amount of extractable materials present, the more TlF needed in the treatment. The upper limit on TlF usage is readily determined by the fact that when a solid TlF phase appears, no further-improvement is obtainable. By the time that this third phase of solid TlF appears, a sufficiently refined oil has been attained. Thus there can be used between a trace amount of TlF and an amount of TlF that will not dissolve completely into the extract phase. Expressing the TlF usage in another way, we can use from 0.1 wt. per cent to about 25 wt. per cent and, in some cases to about 100 wt. per cent, based on the raw oil. The amount of TlF needed to obtain a particular degree of refinement is readily determinable by small scale treatment of samples of the raw oil.

When treating the heavy distillates sufficient liquid HF must be present in the extraction zone to form a separate HF-rich phase, i. e., extract phase. The minimum amount of liquid HF needed will vary somewhat with the type of oil being treated and the extractable materials content of the raw oil. The viscosity of the raw oil affects phase separation and, in general, the more viscousv the raw oil, the more HF needed to obtain good phase separation. The presence of extractable materials in the liquid HF increases the viscosity of the extract phase so that good phase separation may be dicult when treating raw oils containing large amounts of extractable materials with small amounts of HF. When treating light gas oils the minimum HF usage may be as low as l0 volume percent, based on the raw oil. When treating lube stocks such as distillate for the production of S. A. E. 20 oil, as much as 2,0 volume percent of liquid HF may be needed to obtain good phase separation. It is preferred to use more than the bare minimum amount of liquid HF.

As-muchas 1500 volume percent liquid .HF hasbeenused withoutrdetrimentalfeffect.. However, little significant gain ini refinement is1obtained-by usingvery large amounts of liquiclHF.A For-mostraw oils satisfactory phase separation-and-asatisfactory degree-of refinement can be obtained by using from about to about 500.volu1ne percent o'f liquid- HF. It is'preferred to useI between about 30 and-300 volumepercent.

In the-treatment of heavy. distillates viscosity has .an appreciable effect on the cleanness of the phase separation; the viscosity of the heavy distillate can be reduced by, adding an inert diluent thereto. The diluent should be relatively inert to the solvent action of the treating agent and also to thev catalytic action of the treatingagent. Additionally, the diluent should be readilyV separable by distillation from the refined oil, although in some cases it may be desirable to leave thel diluent in the refined oil. Suitable diluents arepentane, hexane, petroleum ether, cyclohexane, various naphtha fractions low in extractable materials, etc. Materials such as heptane or octane can be used when the treating is at about ambient temperatures. However, diluents containing about 6 or more carbon atoms are` readily isomerized and even cracked by our treating agent at temperatures above about 250 F., so that their use at elevated temperatures is undesirable. In general olefinic hydrocarbons are not suitable diluents. The amount of diluent-used will be dependent upon the type of raw oil being charged, but in general will be between about 10 and 200 volume percent based on raw oil. When using a diluent it may be possible to reduce the amount of liquid HF ordinarily used and still obtain a satisfactory phase separation.

When treating heavy distillates the temperature of treatmentrrnay be on the order of those used when treating naphthas. However, in the case of lubricating oils, some improvement in quality can be obtained by operating at temperatures as high as 450-500" F. The HF catalyzed, isomerization, alkylation, cracking and other reactions result in an increase in the amount of liquid HF-soluble material and an improved quality raffinate oil. The lower temperatures of operation should be above the freezing point of the heavy distillate itself or the freezing point of the diluted feed. In general it is preferred to treat heavy distillates at temperatures between about 50 andA 100 F.

Contacting time will be dependent on the type of raw oil, the amount of liquid HF-TlF treating agent and the temperature of operation. In general times between about 5 minutes and 60 minutes in each extraction stage will be sufficient to obtain the desired degree of refining.

The heavy distillate feed to the liquid HF-TlF treating operation can be: various fractions obtained from the distillation of crude oil,` e. g., kerosenes, heater oil, lube oils, etc., or the crude oil itself, or reduced crudes. Another class of materials suitable as a feed may be oils derived from the treatment of the above materials, e. g., rafinates and extracts from the solvent treatment of kerosenes or lube oils. Shale oil, and its various fractions, is a suitable feed to our process. The liquid products from the hydrogenation of coal or the Fischer-Tropsch process are suitable feedsto our process. Appreciable amounts of olefins can be eliminated from olefin-containing feeds by treatment with liquid HF-TlF; the alkylate may or may not be extracted into the extract phase. In general oils containing large amounts of olefins are not a. desirable feed to our process. In general the most suitable feed stocks are petroleum distillates boiling in the heavier-than-gasoline range, i. e'., above about 350 F. and below about 700 F.,` and particularly those distillates derived from high sulfur and high aromatic content crudes, such as, West Texas crude, Winkler crude, etc.

The raffinate phase from the treating of hydrocarbon oils with liquid HF--TIF treating agent will usually contain somel dissolved liquid HF and also some entrained HF;-A small amounts of solid TlF may also be entrained.

The TIF can. be recovered by filtration, by, a coalescing operationor in some cases by distilling the rafiinateoil. The liquid HF Vis readily'removed from the raffinate phase by` distillation at temperatures of about Fl, at atmospheric pressure. In some cases the raffinate may contain minor amounts of alkyl fiuoridesgthese can be readily removed bypercolation through bauxite.

The extract phase obtained from the treatment of hydrocarbonl oils with liquid HF--TlF treating agent is readily decomposed by treatment with water, preferably cold water or ice; the upper layer of extract oilfcan be decanted from the lower aqueous layer. The extractoil contains the extracted materials, i. e., hydrocarbons and/or organic sulfur compounds. The lower aqueous layer consists of a mixture of hydroliuoric acidand TIF. The extract nil can. be freed of traces of' HF by, treatment with dilute caustic. Thismethod is particularly suitable for laboratory operations.

It is preferred to decompose theA extract phase as follows: The extract phase is placed in a vessel, usually pro.- vided with a few fractionation trays, wherein the temperature-of the extract phase, is raised until the HF vaporizes and passes outof the vessel. The top temperature inthe decomposing vessel4 is held at about the-boiling. point of HF-in order to prevent the removal of extract materials along with the HF. In the bottom of the decomposer after theremoval of HF, there exists a slurry of extract materials and solid. finely` divided TlF. This slurry is passed to a filter which retains` the solidTlF. The TlF can be` reused in theprocess. In the case of lower boil-V ing extract materials, the extract materials. may bedistilled-leaving behind the solidTlF. By operating under vacuum, the HF may be removed at low temperatures. It is preferred to'operate atfrom about 200 to 500 F.; the lowest possible temperature is preferred because of the. side-reactions resultingfromY the catalytic action of the treating agent. Where. it is desired to avoid sidereactions` inthe extract phase, the decomposer may be operated under vacuum in order to remove a major part ofv the-liquid HF at temperatures below about 100 F.; then the partially denuded extract phase is heated to from about200 to y500 F. to removethe remainder oftheHF.

Normally the raffinate from the heavy distillate treatment processwill be the desired product. However, the low: sulfur, low aromatic content thereof makes the refined oil avery suitable feed to a catalytic cracking operation; thus our process may be used totreat cycle'gasroils whichare low quality catalytic crackingfeeds in order to improve their'suitability fory catalytic cracking. These cycle oils may be derived from thermalcracking, coking or catalytic cracking.

It has been found'that the organic sulfur compounds present in the extract from the treatment of heavy naphtha and gas oils boiling between about 350 and 600 F. are ver-yy readily catalytically cracked to produce a high octane, low sulfur product. Particularly good results are obtained'whenthe extractisfractionated and that portion boiling below about 450 F. ischarged to the catalytic cracking operation.

It has also been discovered that a separation can be made between ethylbenzene and xylene by the treatment of amixture of ethylbenzene and xylene, e. g., a mixed Ca aromatic hydrocarbon fraction with liquid I-IF--TlF treating agent. It` has been found that by contacting said mixturewith an amount of TlF of about 1 mol per mol of xylen'e present therein, and sufficient liquid HF to participate in they complex and also to dissolve said complex to forma separate extract' phase, a raffinate phase and an extract phase are formed. The mol ratio of ethylbenzene/ xylene in the raffinate is higher than the ratio in the feed. By the use-of multi-stage contacting, it is possible to produceV a high purity ethylbenzene raffinate product and a high purity xylene extract product.,

It has also'beendiscovered that a more economical seperation. of ethylbenzene from xylene can` be obtained.` by

extractive distillation procedure. In this procedure the feed mixture of ethylbenzene and xylene is introduced at about the vertical mid-point of a fractionation column and liquid HF-TlF agent introduced at a higher point in said column. Temperature and pressure are so regulated in the column that there is withdrawn overhead a stream of HF vapor and aromatic hydrocarbon vapor. The aromatic hydrocarbon vapor is cooled to form a high purity ethylbenzene fraction. From the bottom of the tower is withdrawn a mixture of high purity xylene and solid TlF, which mixture may be readily separated by filtration. In the extractive distillation operation, about 1 mol of TlF is used per mol of xylene.

The results obtainable by this process in the separation of lower molecular weight mononuclear aromatics from naphthas is illustrated by the following example: In this example the contacting was carried out in a carbon steel reactor equipped with a 1725 R. P. M. stirrer. An amount of solid thallium formate was introduced into the reactor and an excess of liquid HF over the stoichiometric quantity was introduced. A reaction occurred at room temperature as evidenced by increase of pressure in the reactor. When the reaction had stopped as evidenced by constant pressure in the reactor, the formic acid and excess HF were pumped out of the reactor leaving behind solid thallium monofluoride. The feed to the example consisted of a synthetic blend of 60 volume percent n-heptane, 20 volume percent m-xylene and 20 volume percent of p-xylene. The mol ratio of xylene to thallium was 2.3. An amount of liquid HF equal to 120 volume percent on total feed was introduced into the reactor and then the feed was introduced therein. The liquid HF-TlF feed mixture was agitated at about 50 F. for 60 minutes. The contents of the reactor were then permitted to settle for l minutes before being withdrawn.

The lower extract phase was withdrawn into a vessel containing crushed ice; the hydrocarbons from the decomposed extract phase were decanted away from the aqueous layer. These hydrocarbons were washed with caustic to eliminate traces of HF and then were distilled in a 30- plate laboratory column to obtain narrow boiling fractions. In this example only one narrow boiling fraction was obtained. The rainate phase was washed with aqueous caustic to remove entrained HF and was then distilled to obtain a single narrow boiling fraction. The purity and the compositions of these fractions were determined by a combination of infrared analysis, boiling point, specific gravity and refractive index.

Analysis of the ranate and extract phase showed that 64 mol percent of the aromatics present in the feed had been extracted into the extract phase. This corresponds to xylene/TlF mol ratio of 1.29. The apparent ability of the TlF to extract more than an equal molar amount of xylene is due to the solubilizing effect of the complex on the ability of liquid HF to dissolve aromatic hydrocarbons.

Within the limits of experimental error the molar distribution of m-xylene and p-xylene in the raflinate and in the extract was unchanged over that of the feed xylenes.

The annexed drawing which forms a part of this specification shows an illustrative embodiment ofone method of utilizing this process. This embodiment illustrates the extraction of benzene, toluene and Cs aromatic hydrocarbons from a hydroformate naphtha boiling below about 325 F. It is to be understood that many pieces of process equipment such as pumps and valves have been omitted from this embodiment. These pieces of equipment may readily be added thereto by those skilled in the art.

The feed to the embodiment consists of a debutanized hydroformate having an end point of 325 F. This hydroformate contains about 55% of benzene, toluene and Cs aromatics, about 3% of olefins and about 0.01 wt. percent sulfur.

The feed from source 11 passes through line 12 into 1mixer 13. In mixer 13 the feed is thoroughly contacted to be described later; this extract phase-consisting of liquid HF, complex, an excess of soluble TlF and dissolved non-aromatic hydorcarbons-is passed into line 12 by way of line 14. Mixer 13 is provided with a heat exchanger 16 which permits the temperature of contacting to be maintained at the desired point. In this illustration contacting is carried out at 75 F. and at about 25 p. s. i. g. for about 15 minutes.

From mixer 13 the mixed feed-solvent passes through line 17 into settler`18. In settler 18 the mixed feed-solvent separates into a rainate phase consisting mainly of nonaromatic hydrocarbons and a small percentage of aromatic hydrocarbons and an extract phase consisting of liquid HF, complex, excess soluble TlF and minor amounts of non-aromatic hydrocarbons. The raffinate from settler 18 is withdrawn through line 19 and is passed into line 21.

Liquid HF from source 22 is passed through line 23 into vessel 24 where it meets TlF from source 26 and line 27 and also recycled liquid HF-TlF mixture. In order to recover the aromatics present in the feed in the least number of stages We use 1.2 mols of TlF in this particular illustration, all of which will be present in mixer 31. The liquid HF must be present in an amount great enough to form the complex and to dissolve the complex once formed. More than this amount is desirable as phase separation and aromatic selectivity are facilitated by a larger volume of liquid HF. In this particular illustration we use 300 volume percent of liquid HF based upon the feed stock charged to the process. The liquid HF-TlF mixture from vessel 24 passes into line 21 where it meets the raffinate phase from settler 18 and on into mixer 31. Mixer 31 is provided with a heat exchanger 32 for control of the temperature of contacting; herein we operate at about 75 F., the same as that used in the first contacting stage in mixer 13. The liquid HF--TlF treating agent and the first raffinate phase are intimately contacted for about 15 minutes in mixer 31. From mixer 31 the mixture passes through line 33 into settler 34. In settler 34 a second rafiinate phase containing little or no aromatic hydocarbons is separated from the extract phase. This second raffinate phase from settler 34 passes through line 36 into stripper 37 which is provided with reboiler 38. In stripper 37 the HF dissolved in the second raffinate phase is removed overhead through line 39; stripper 37 may be operated at about 200 .to 400 F. at about 25 to 150 p. s. i, g. In heat exchanger 41 the HF is condensed to a liquid and may be recycled to the process through line 42. Some low boiling material may azeotrope with the HF and this may be recycled along with the HF. However, if this material is not wanted in the extraction step, it can be removed by a settling operation (not shown) from the liquid HF and sent to the non-aromatic product. The non-aromatic portion of the feed stock passes out of stripper 37 through line 46 to storage not shown. These non-aromatic hydrocarbons are almost entirely isoparaffins of high octane number and are valuable as gasoline blending material. The very slight fluoride content thereof can be eliminated by percolation through bauxite.

From settler 34 the extract phase is sent to the first contacting stage through line 14. By this two-stage countercurrent contacting procedure, we are able to recover substantially all the aromatic hydrocarbons present in the feed stock.

From settler 1S the extract phase is passed through line S1 into line 52 where it meets pentane from source 53. From line 52 the extract phase-pentane mixture passes into mixer 54. The pentane usage will be dependent upon the percent of non-aromatics in the extract phase. We have found that particularly good results are obtained when between 50 and 200 volume percent based on total hydrocarbons present in the extract phase is used. From mixer 54 the pentane-extract phase mixture passes through line 56 into settler 57. From settler S7fa raffinate phase consisting of pentane and substantially all the nonaromatics present in the extract phase from line 51 is withdrawn by line 58. The material in line 58 may be withdrawn from the system through valved line 59 or a portion may be recycled to the washing step through valved line 61 and line 52. In order to avoid a buildup of interfering non-aromatic hydrocarbons in the washed extract phase, we prefer that the contaminated pentane be discarded to gasoline blending stock.

From settler 57 the washed extract phase passes through line 66 through heat exchanger 67 and line 68 into vessel 69. Vessel 69, commonly called a decomposer, is provided with a heat exchanger 71 and a number of bubble trays in order to obtain some fractionation, In decomposer 69 the HF and pentane are passed overhead through line 74 and are condensed by heat exchanger 75. The HF-pentane mixture passes from line 76 into settler 77 where two phases are formed. The upper pentane layer passes out through line 78 to gasoline blending stock. The lower HF layer passes out of settler 77 through line 79. The decomposer 69 is maintained at a top temperature below the boiling point of benzene in order to keep all the aromatics in the liquid state in decomposer 69. We have found that a suitable top temperature for the operation of decomposer 69 is between about 100 and 140 F., at atmospheric pressure operation. Higher temperatures may be used if the decomposer is operated at super atmospheric pressure. The bottom temperature of decomposer 69 can be between 200 and 500 F. and about the mid-boiling point of the aromatics is a suitable temperature.

In the bottom of decomposer 69 a slurry of solid, nely divided TlF and aromatic hydrocarbons is formed. This slurry passes out of decomposer 69 through valved line 81 into filter 82. Filter 82 may be any type which can be made of liquid HF-resistant materials and HF-vapor tight, and which is able to retain finely divided solids. In this ow sheet we show only one iilter. However, normally two or more filters will be used in order to permit continuous operation and the presence of additional filters is to be understood in this particular illustration of our process. Filter 82 retains the solid TlF and the aromatics pass out through valved line 83.

Liquid HF from settler 77 passes through valved line 79 into filter S2; the TIF in the filter is removed by the liquid HF and the liquid HF-TlF mixtures passes out of filter 82 through valved line 86 and is recycled to vessel 24 through line 87.

From filter 82 the aromatics pass through valved line 33, through heat exchanger 91 and through line 92 into fractionator 93, which fractionator is equipped with reboiler 94. In fractionator 93 nitration-grade benzene is taken overhead through line 97 to storage not shown. The remaining aromatics pass out of the bottom of the fractionator 93 through line 99, heat exchanger 101 and line 102 into fractionator 103.

Fractionator 103, equipped with reboiler 104, separates the aromatics from line 102 into a nitration-grade toluene fraction, tal-:en overhead through line 106 to storage not shown; and a bottoms fraction consisting of C8 aromatics and higher boiling polyalkyl aromatics.

The bottoms from fractionator 103 pass out through line 107, heat exchanger 108 and line 109 into fractionator 111, which is equipped with reboiler 112. The C8 aromatics, consisting of o-xylene, m-xylene, p-xylene and ethylbenzene pass out of fractionator 111 through line 114 to storage not shown. From the bottom of fractionator 111 through line 116 higher boiling polyalkyl aromatics are withdrawn. These higher boiling aromatics were formed by the alkylation of lower boiling aromatics with the olcns present in the feed by the catalytic action of the liquid HF. i 'i This embodiment of our invention shows how simply we are able to separate benzene, toluene and Cs aromatics from a mixed hydrocarbon and by simple fractional distillation recover nitration-grade benezene and toluene and mixed Ca aromatic hydrocarbons separately.

When it is desired to recover aromatic hydrocarbons from naphthas containing substantial amounts of sulfur, e. g., 0.1 or more, the feed naphtha should be given a desulfurization treatment prior to contacting with liquid HF-TlF treating agent. Many desulfurization methods are known. However, it is preferred to use the method of U. S. 2,450,588. Very briey, this method involves the treatment of naphtha with liquid HF at ambient temperatures to produce a low sulfur rainate product and a high sulfur HF extract phase. This raflinate product is suitable for treatment in the process of this invention.

Thus having described the invention, what is claimed l. A process for refining a mixed hydrocarbon oil, which process comprises contacting said oil with TlF in the presence of suicient liquid HF to form an extract phase and separating a raffinate phase from said extract phase.

2. The process of claim 1 wherein said contacting is carried out at a temperature below about 500 F.

3. The process of claim l wherein said contacting is carried out in the presence of an inert diluent.

4. A process for the treatment of a hydrocarbon oil which contains extractable materials, which process comprises contacting said oil at a temperature below about 500 F. with an eiective amount of TlF in the presence of sufficient liquid HF to form an extract phase and separating a rainate phase from said extract phase.

5. The process of claim 4 wherein in said contacting step said liquid HF is present in an amount from 10 to 1500 volume percent based on said oil and said TlF is present in an amount from at least some to about the limit of solubility of TlF in said extract phase.

6. The process of claim 5 wherein said temperature is less than about 200 F.

7. The process of claim 4 wherein said extractable materials are selected from the group consisting of mononuclear aromatics, polynuclear aromatics, organic sulfur compounds and phenolic compounds.

8. The process of claim 4 wherein said oil is a petroleum distillate boiling within the range of about 350 to 700 F.

9. A process for refining a lubricating oil stock, which process comprises the steps of contacting said stock with from about 0.1 to 25 weight percent of TlF in the presence of 30 to 300 volume percent of liquid HF, both based on said stock, at a temperature from about to 100 F. for an effective length of time and separating a radinate phase from an extract phase.

l0. The process of claim 9 wherein said contacting is carried out in the presence of from about 10 to 200 volume percent, based on said stock, of an inert diluent.

l1. A proces for the extraction of aromatic hydrocarbons from a feed that boils below about 450 F. and contains a mixture of aromatic and non-aromatic hydrocarbons, which process comprises contacting said feed with a treating agent consisting of about one mol of thallium lliioride per mol of aromatic to be extracted and suicient liquid HF to participate in the formation of a complex `containing aromatics, TlF and HF and to dissolve said complex, thereby forming an extract phase, separating an upper rainate phase consisting essentially of hydrocarbons and some HF from said lower extract phase containing liquid HF, complex, and dissolved hydrocarbons, and treating said extract phase to recover the hydrocarbons.

12. The process of claim l1 wherein the amount of liquid .HF in said treating agent is between about 10 and 1500 vvolume percent, based on said feed mixture, and the temperature of contacting is below about 250 F.

13. The process of claim 11 wherein said feed is substantially vfree of organic-sulfur compounds and phenolic compounds- 14. The process of claim l1 wherein said feed boils below about 325" F. and is substantially free of organicsulfur compounds and phenolic compounds.

15. A process for the extraction of aromatic hydro carbons from a feed that boils below about 450 F. and that contains a mixture of aromatic and non-aromatic hydrocarbons and substantially no organic-sulfur compounds and/or phenolic compounds, which process comprises contacting said feed with a treating agent, at a temperature between about 60 F. and about 250 F., separating a rafiinate phase, containing a smaller percentage of aromatics than said feed, from an extract phase containing treating agent, aromatics and some non-aromatics, and recovering said hydrocarbons from said extract phase, wherein said treating agent consists essentially of from 10 to 1500 volume percent of liquid HF, based on said feed, and about one mol of TlF per mol of aromatics to be extracted from said feed.

16. The process of claim 15 wherein the amount of liquid HF is from about 100 to 500 volume precent and the amount of TlF is between about 0.1 and the limit of solubility of TIF in said extract phase.

17. The process of claim 15 wherein said extract phase is washed with sufficient diluent hydrocarbon, possessing a boiling point that permits easy separation from said aromatics, to remove substantially all of said non-aromatics from said extract phase, separating a second rainate consisting of said diluent and said non-aromatics from a second extract phase containing treating agent, said extract aromatics and diluent hydrocarbons and recovering said hydrocarbons from said second extract phase.

18. The process of claim 17 wherein said diluent is pentane.

19. A process for the treatment of a substantially sulfurfree and phenolic-compound free naphtha boiling below about 325 F. and which naphtha consists of benzene, toluene, mixed C8 aromatics, and non-aromatics and which process comprises intimately contacting said naphtha for from about 5 minutes to 6 hours at a temperature between about 0 and 160 F. with a treating agent consisting of liquid HFin amount 100 to 500 volume percent based on said naphtha, and TIF, in amount from about 0.8 to 1.2 mols per mol of aromatics in said naphtha, separating a rainate phase containing non-extracted hydrocarbons from an extract phase containing treating agent, aromatics and some non-aromatics, and recovering said aromatics and non-aromatics from said extract phase.

20. A process for the extraction of aromatic hydrocarbons from a naphtha which boils below 450 F. and contains substantial amounts of organic-sulfur compounds, aromatics and non-aromatics, which process comprises in a first step treating said naphtha to remove substantially all of said organic sulfur compounds without removing substantial amounts of aromatics and contacting said desulfurized naphtha at a temperature below about 250 F. with a treating agent consisting of 1,00 to 500 volume percent of liquid HF, based on said desulfurized naphtha, and from about 0.1 to 1.2 mols of TIF per mol of aromatic in said desulfurizing naphtha, separating a raflinate phase from an extract phase consisting of treating agent, aromatics and some non-aromatics and recovering said aromatics and non-aromatics from said extract phase.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,762 Frey June 19, 1945 

1. A PROCESS FOR REFINING A MIXED HYDROCARBON OIL, WHICH PROCESS COMPRISES CONTACTING SAID OIL WITH TIF IN THE PRESENCE OF SUFFICIENT LIQUID HF TO FORM AN EXTRACT 